A circuit for measuring composite frequency signals

Abstract

The present invention relates to the field of frequency signal measurement technology, and in particular to a circuit for measuring composite frequency signals, comprising a proximity switch detection circuit, a voltage amplitude frequency signal input detection circuit, a transistor frequency signal input detection circuit, and an MCU. The proximity switch frequency signal is processed by the proximity switch detection circuit and converted into a TTL level signal, which is output to the MCU. The voltage amplitude frequency signal is converted into a frequency square wave signal by the voltage amplitude frequency signal input detection circuit and output to the MCU. The transistor frequency signal is converted into a TTL level signal by the transistor frequency signal input detection circuit and output to the MCU. The present invention is suitable for most industrial frequency measurement applications and solves problems such as measurement errors or inability to measure caused by variable frequency amplitudes and multiple signal input types. Frequency signals are input through different ports, and different signal types can be matched without jumpers, thereby improving product versatility and reducing costs.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency signal measurement, and in particular to a circuit for measuring composite frequency signals. Background Art

[0002] With the rapid development of industrial intelligent instrumentation technology, a wider variety of frequency inputs are being used in various industrial applications, including on-site NAMUR proximity switch frequency signals, transistor (NPN or PNP) frequency signals, and voltage amplitude frequency signal inputs. Due to the varying driving voltages and operating principles of different frequency signal types, the standard driving voltage for NAMUR frequency signals is 8.2V, with a current ≥2.1mA in the ON state and ≤1.2mA in the OFF state. Transistor frequency signals typically have a driving voltage of 24V and use an OC gate to output high and low levels. Voltage amplitude frequency signals are active frequency signals, typically directly outputting an AC frequency signal from a sensor. A single frequency (conventional voltage amplitude) detection method no longer meets practical needs, primarily due to the limited applicability of voltage amplitude detection technology solutions and the high cost of single-use development.

[0003] Furthermore, current frequency sensor signal detection is susceptible to interference from field spikes and the sensor's output frequency amplitude. Typical circuit designs are tailored to the actual high and low frequency ranges in the field. If the sensor's output frequency amplitude falls outside the circuit's design range, the detection circuit may be inaccurate or unable to detect the signal. Furthermore, different frequency signal types require different ports and even jumpers, resulting in poor product versatility and high development costs. Summary of the Invention

[0004] The invention provides a circuit for composite frequency signal measurement, which is adaptive to multiple frequency signal inputs, has high versatility and low development cost.

[0005] In order to achieve the purpose of the present invention, the technical solution adopted is: a circuit for measuring a composite frequency signal, including a proximity switch type detection circuit, a voltage amplitude frequency signal input detection circuit, a transistor frequency signal input detection circuit and an MCU, wherein the proximity switch frequency signal is processed by the proximity switch type detection circuit and converted into a TTL level signal and output to the MCU; the voltage amplitude frequency signal is converted into a frequency square wave signal by the voltage amplitude frequency signal input detection circuit and output to the MCU; the transistor frequency signal is converted into a TTL level signal by the transistor frequency signal input detection circuit and output to the MCU; the MCU is used to measure the period of the frequency signal to obtain the frequency value.

[0006] As an optimized solution of the present invention, the proximity switch type detection circuit includes an excitation source, a first filtering circuit, a first sampling circuit and a first comparison circuit. The excitation source is used to provide working power for the proximity switch. The proximity switch frequency signal is filtered out by the first filtering circuit to remove the noise and then output to the first sampling circuit. The first sampling circuit fixes the amplitude of the proximity switch frequency signal from which the noise is filtered out and then outputs it to the first comparison circuit. The first comparison circuit is used to convert the signal output by the first sampling circuit into a TTL level signal and output it to the MCU.

[0007] As an optimization solution of the present invention, the first filtering circuit is the first capacitor C1, the first sampling circuit is the first resistor R1, and the first comparison circuit is the first comparator U1. The proximity switching frequency signal is filtered out of interference signals through the first capacitor C1. The first resistor R1 fixes the amplitude of the proximity switching frequency signal after filtering out the interference signal and outputs it to the input end of the first comparator U1 for processing and then outputs a TTL level signal.

[0008] As an optimized solution of the present invention, a second filtering circuit is provided between the first sampling circuit and the first comparing circuit.

[0009] As an optimized solution of the present invention, the voltage amplitude and frequency signal input detection circuit includes a port protection circuit, a DC isolation circuit, a limiting circuit, a second comparison circuit and a shaping circuit. The voltage amplitude and frequency signal is protected by the port protection circuit and then passes through the DC isolation circuit to remove the DC component. The signal output from the DC isolation circuit is then clamped by the limiting circuit to clamp the amplitude voltage. The signal output from the limiting circuit passes through the second comparison circuit to convert the voltage frequency signal into a TTL level frequency signal, and finally is converted into a frequency square wave signal by the shaping circuit and output to the MCU.

[0010] As an optimized solution of the present invention, the port protection circuit includes a fourth resistor R4 and a fifth resistor R5, the DC isolation circuit includes a fourth capacitor C4, the limiting circuit is a sixth resistor R6, and the second comparison circuit is a second comparator U2. The input voltage amplitude frequency signal is sequentially limited by the fourth resistor R4 and the fifth resistor R5 and then input into the fourth capacitor C4. The fourth capacitor C4 removes the DC component of the input signal and outputs the clamped amplitude voltage to the sixth resistor R6. The voltage output from the sixth resistor R6 is converted into a TTL level frequency signal through the second comparator U2.

[0011] As an optimized solution of the present invention, a third filtering circuit is provided between the amplitude limiting circuit and the second comparison circuit.

[0012] As an optimized solution of the present invention, the transistor frequency signal input detection circuit includes a voltage driving circuit, a third sampling circuit, a PNP type comparison circuit and an NPN type comparison circuit. The voltage driving circuit is used to provide working power for the transistor, and the transistor frequency signal enters the PNP type comparison circuit or the NPN type comparison circuit after passing through the third sampling circuit.

[0013] As an optimized solution of the present invention, the third sampling circuit is the eighth resistor R8, the PNP type comparison circuit is the third comparator U3, and the NPN type comparison circuit is the fourth comparator U4. The transistor frequency signal is converted into a voltage through the eighth resistor R8. The third comparator U3 or the fourth comparator U4 compares the converted voltage of the eighth resistor R8 with its own pre-set voltage, thereby determining whether the transistor is NPN type or PNP type, and outputting a TTL level signal.

[0014] As an optimized solution of the present invention, a fourth filtering circuit is provided between the third sampling circuit and the PNP type comparison circuit.

[0015] The present invention has positive effects: 1) The present invention supports multiple frequency signal input detection and adapts to multiple different frequency input signal types;

[0016] 2) The present invention is suitable for most frequency measurement industrial occasions, and solves the problems of measurement error or inability to measure caused by non-fixed frequency amplitude and multiple signal input types. Frequency signals are input through different ports, and different signal types can be matched without jumpers, realizing the multi-functionality of one machine, reducing the variety of products, improving product versatility and reducing development costs.

[0017] 3) The present invention can simultaneously support the detection of multiple frequency signal inputs. When multiple frequency signals are not input simultaneously, the number of terminals can be reduced by multiplexing the terminals, thereby further reducing the development cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 It is the overall structural diagram of the present invention;

[0020] Figure 2 It is the structural block diagram of the proximity switch type detection circuit;

[0021] Figure 3 The block diagram of the proximity switch type detection circuit with the addition of a filter circuit;

[0022] Figure 4 This is the circuit schematic diagram of the proximity switch type detection circuit;

[0023] Figure 5This is a structural block diagram of the voltage amplitude frequency signal input detection circuit;

[0024] Figure 6 The structural block diagram of the voltage amplitude frequency signal input detection circuit for increasing the filtering circuit;

[0025] Figure 7 This is a circuit schematic diagram of a voltage amplitude frequency signal input detection circuit;

[0026] Figure 8 This is a structural block diagram of a transistor frequency signal input detection circuit;

[0027] Figure 9 A structural block diagram of a transistor frequency signal input detection circuit for adding a filter circuit;

[0028] Figure 10 This is the circuit schematic diagram of the transistor frequency signal input detection circuit.

[0029] Among them: 1. proximity switch type detection circuit, 2. voltage amplitude frequency signal input detection circuit, 3. transistor frequency signal input detection circuit, 11. excitation source, 12. first filtering circuit, 13. first sampling circuit, 14. first comparison circuit, 15. second filtering circuit, 21. port protection circuit, 22. DC isolation circuit, 23. limiter circuit, 24. second comparison circuit, 25. shaping circuit, 26. third filtering circuit, 31. voltage driving circuit, 32. third sampling circuit, 33. PNP type comparison circuit, 34. NPN type comparison circuit, 35. fourth filtering circuit. DETAILED DESCRIPTION

[0030] like Figure 1 As shown, the present invention discloses a circuit for measuring composite frequency signals, comprising a proximity switch detection circuit 1, a voltage amplitude frequency signal input detection circuit 2, a transistor frequency signal input detection circuit 3, and an MCU. The proximity switch frequency signal is processed by the proximity switch detection circuit 1 and converted into a TTL level signal, which is output to the MCU. The voltage amplitude frequency signal is converted into a frequency square wave signal by the voltage amplitude frequency signal input detection circuit 2 and output to the MCU. The transistor frequency signal is converted into a TTL level signal by the transistor frequency signal input detection circuit 3 and output to the MCU. The MCU is used to measure the period of the frequency signal and calculate the frequency value based on f = 1 / T. The proximity switch detection circuit 1, the voltage amplitude frequency signal input detection circuit 2, and the transistor frequency signal input detection circuit 3 operate independently without interfering with each other, and different input ports can be used to match different frequency input signal types.

[0031] like Figure 2As shown, the proximity switch detection circuit 1 includes an excitation source 11, a first filtering circuit 12, a first sampling circuit 13 and a first comparison circuit 14. The excitation source 11 is used to provide working power for the proximity switch. The proximity switch frequency signal is filtered out by the first filtering circuit 12 and then output to the first sampling circuit 13. The first sampling circuit 13 fixes the amplitude of the proximity switch frequency signal after filtering out the noise and then outputs it to the first comparison circuit 14. The first comparison circuit 14 is used to convert the signal output by the first sampling circuit 13 into a TTL level signal and output it to the MCU. Figure 3 As shown, a second filtering circuit 15 is provided between the first sampling circuit 13 and the first comparing circuit 14 .

[0032] like Figure 4 As shown, the first filter circuit 12 is a first capacitor C1, the first sampling circuit 13 is a first resistor R1, and the first comparison circuit 14 is a first comparator U1. The proximity switching frequency signal is filtered out of interference signals by the first capacitor C1. The first resistor R1 fixes the amplitude of the proximity switching frequency signal after filtering out interference signals and outputs it to the input end of the first comparator U1. The first comparator U1 processes the signal and outputs a TTL level signal. The second filter circuit 15 includes a second-order filter circuit consisting of a second resistor R2, a third resistor R3, a second capacitor C2, and a third capacitor C3.

[0033] like Figure 5 As shown, the voltage amplitude frequency signal input detection circuit 2 includes a port protection circuit 21, a DC isolation circuit 22, a limiter circuit 23, a second comparison circuit 24, and a shaping circuit 25. After the voltage amplitude frequency signal is protected by the port protection circuit 21, it passes through the DC isolation circuit 22 to remove the DC component. The signal output from the DC isolation circuit 22 is then clamped by the limiter circuit 23 to clamp the amplitude voltage. The signal output from the limiter circuit 23 is converted into a TTL level frequency signal by the second comparison circuit 24. Finally, it is converted into a frequency square wave signal by the shaping circuit 25 and output to the MCU. Figure 6 As shown, a third filter circuit 26 is provided between the amplitude limiting circuit 23 and the second comparison circuit 24 .

[0034] like Figure 7 As shown, the port protection circuit 21 includes a fourth resistor R4 and a fifth resistor R5, the DC blocking circuit 22 includes a fourth capacitor C4, the amplitude limiting circuit 23 is a sixth resistor R6, and the second comparison circuit 24 is a second comparator U2. The input voltage amplitude frequency signal is sequentially current-limited by the fourth resistor R4 and the fifth resistor R5 before being input to the fourth capacitor C4. The fourth capacitor C4 removes the DC component of the input signal and outputs the clamped amplitude voltage to the sixth resistor R6. The voltage output from the sixth resistor R6 is converted into a TTL level frequency signal by the second comparator U2. The third filter circuit 26 includes a seventh resistor R7 and a fifth capacitor C5.

[0035] like Figure 8 As shown, the transistor frequency signal input detection circuit 3 includes a voltage driving circuit 31, a third sampling circuit 32, a PNP type comparison circuit 33 and an NPN type comparison circuit 34. The voltage driving circuit 31 is used to provide working power for the transistor. The transistor frequency signal enters the PNP type comparison circuit 33 or the NPN type comparison circuit 34 after passing through the third sampling circuit 32. The PNP type comparison circuit 33 or the NPN type comparison circuit 34 pre-sets different comparison voltages to distinguish the NPN type or PNP type of the transistor. If the frequency voltage is high, the NPN type comparison circuit 34 will work, otherwise the PNP type comparison circuit 33 will work. Figure 9 As shown, a fourth filtering circuit 35 is provided between the third sampling circuit 32 and the PNP type comparison circuit 33 .

[0036] like Figure 10 As shown, the third sampling circuit 32 is the eighth resistor R8, the PNP type comparison circuit 33 is the third comparator U3, and the NPN type comparison circuit 34 is the fourth comparator U4. The transistor frequency signal is converted into a voltage through the eighth resistor R8. The third comparator U3 or the fourth comparator U4 compares the converted voltage of the eighth resistor R8 with its own pre-set voltage to determine whether the transistor is NPN type or PNP type, and outputs a TTL level signal. After current limiting, the transistor frequency signal is converted into a voltage by the eighth resistor R8, filtered by the fourth filter circuit 35 composed of the ninth resistor R9 and the sixth capacitor C6, and then compared with the third comparator U3 or the fourth comparator U4 at the back end. When the transistor model is NPN type, the transistor frequency signal voltage is a high value, that is, the high level is greater than 8V. The preset voltage of the fourth comparator U4 is 8V, so it is compared with the fourth comparator U4; when the transistor model is PNP type, the transistor frequency signal voltage is a low value, that is, the high level is less than 4V. The preset voltage of the third comparator U3 is 4V, so it is compared with the third comparator U3; because the comparison voltage of the NPN transistor and the PNP transistor is different, the two are independent of each other during measurement and do not interfere with each other.

[0037] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A circuit for measuring a composite frequency signal, characterized in that: The invention comprises a proximity switch type detection circuit (1), a voltage amplitude frequency signal input detection circuit (2), a transistor frequency signal input detection circuit (3) and an MCU. The proximity switch frequency signal is processed by the proximity switch type detection circuit (1) and converted into a TTL level signal and output to the MCU; the voltage amplitude frequency signal is converted into a frequency square wave signal by the voltage amplitude frequency signal input detection circuit (2) and output to the MCU. The transistor frequency signal is converted into a TTL level signal by a transistor frequency signal input detection circuit (3) and output to the MCU; the MCU is used to measure the period of the frequency signal to obtain the frequency value; The voltage amplitude frequency signal input detection circuit (2) comprises a port protection circuit (21), a DC isolation circuit (22), a limiter circuit (23), a second comparison circuit (24) and a shaping circuit (25). The voltage amplitude frequency signal is protected by the port protection circuit (21) and then passes through the DC isolation circuit (22) to remove the DC component. The signal output from the DC isolation circuit (22) is then clamped by the limiter circuit (23). The signal output from the limiter circuit (23) is converted into a TTL level frequency signal by the second comparison circuit (24). Finally, the signal is converted into a frequency square wave signal by the shaping circuit (25) and output to the MCU. The port protection circuit (21) includes a fourth resistor R4 and a fifth resistor R5, the DC isolation circuit (22) includes a fourth capacitor C4, the amplitude limiting circuit (23) is a sixth resistor R6, and the second comparison circuit (24) is a second comparator U2. The input voltage amplitude frequency signal is sequentially limited by the fourth resistor R4 and the fifth resistor R5 and then input to the fourth capacitor C4. The fourth capacitor C4 removes the DC component of the input signal and outputs the clamped amplitude voltage to the sixth resistor R6. The voltage output from the sixth resistor R6 is converted into a TTL level frequency signal by the second comparator U2. The transistor frequency signal input detection circuit (3) comprises a voltage driving circuit (31), a third sampling circuit (32), a PNP type comparison circuit (33) and an NPN type comparison circuit (34); the voltage driving circuit (31) is used to provide a working power supply for the transistor; the transistor frequency signal enters the PNP type comparison circuit (33) or the NPN type comparison circuit (34) after passing through the third sampling circuit (32); The third sampling circuit (32) is an eighth resistor R8, the PNP type comparison circuit (33) is a third comparator U3, and the NPN type comparison circuit (34) is a fourth comparator U4. The transistor frequency signal is converted into a voltage by the eighth resistor R8. The third comparator U3 or the fourth comparator U4 compares the voltage converted by the eighth resistor R8 with its own pre-made voltage, thereby judging whether the transistor is an NPN type or a PNP type, and outputting a TTL level signal.

2. The circuit for measuring a composite frequency signal according to claim 1, wherein: The proximity switch type detection circuit (1) comprises an excitation source (11), a first filtering circuit (12), a first sampling circuit (13) and a first comparison circuit (14). The excitation source (11) is used to provide a working power supply for the proximity switch. The proximity switch frequency signal is filtered out by the first filtering circuit (12) to remove the noise therein and then output to the first sampling circuit (13). The first sampling circuit (13) fixes the amplitude of the proximity switch frequency signal after the noise is filtered out and then outputs it to the first comparison circuit (14). The first comparison circuit (14) is used to convert the signal output by the first sampling circuit (13) into a TTL level signal and output it to the MCU.

3. The circuit for measuring a composite frequency signal according to claim 2, wherein: The first filtering circuit (12) is a first capacitor C1, the first sampling circuit (13) is a first resistor R1, and the first comparison circuit (14) is a first comparator U1. The proximity switching frequency signal passes through the first capacitor C1 to filter out interference signals. The first resistor R1 fixes the amplitude of the proximity switching frequency signal after filtering out the interference signals and outputs it to the input end of the first comparator U1 for processing and then outputs a TTL level signal.

4. A circuit for measuring a composite frequency signal according to claim 2 or 3, characterized in that: A second filtering circuit (15) is provided between the first sampling circuit (13) and the first comparing circuit (14).

5. The circuit for measuring a composite frequency signal according to claim 1, wherein: A third filtering circuit (26) is provided between the amplitude limiting circuit (23) and the second comparison circuit (24).

6. The circuit for measuring a composite frequency signal according to claim 1, wherein: A fourth filtering circuit (35) is provided between the third sampling circuit (32) and the PNP type comparison circuit (33).

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